1. Technical Field
The present disclosure relates to a hydraulic brake system, and more particularly, to a hydraulic brake system capable of reducing pressure pulsation caused by operation of a piston pump driven by a hydraulic motor in operation of the hydraulic brake system.
2. Description of the Related Art
In general, a hydraulic brake system refers to a braking system operated by hydraulic pressure.
Brake systems include an anti-lock brake system (ABS) that prevents slippage of a wheel during braking, a brake traction control system (BTCS) that prevents slippage of a driven wheel upon rapid start or rapid acceleration of a vehicle, a vehicle dynamic control system (VDC) that is a combination of the anti-lock brake and traction control systems and maintains a stable driving state of a vehicle by controlling pressure of a brake liquid, etc.
Such a hydraulic brake system includes a master cylinder for generating a desired pressure for braking, a plurality of electronic valves for controlling hydraulic braking pressure transmitted to wheel brakes of a vehicle, a low pressure accumulator for temporarily storing oil, a hydraulic motor and pumps for pumping out the oil temporarily stored in the low pressure accumulator, orifices for reducing pressure pulsation of the oil pumped by the pumps, an electronic control unit (ECU) for electrically controlling the electronic valves and the pump, and the like. Further, a valve assembly of the electronic valves, the accumulator, the pumps, the hydraulic motor, and the like are installed in an aluminum hydraulic block (modulator block). The ECU is connected to the hydraulic block and includes an ECU housing which receives a coil assembly of the electronic valves and a circuit board.
Recently, since driving comfort has become a major concern in designing a vehicle, there is a need to enhance driving comfort.
In the hydraulic brake system described above, although the orifice disposed near an outlet port of each pump reduces pressure pulsation caused by operation of the pump in to a process of multiplying braking pressure, there is difficulty achieving complete reduction of the pressure pulsation since the orifice is provided to control a cross-sectional area of a flow passage for the purpose of damping reduction.
Further, pressure pulsation may be reduced by increasing the number of pistons of the pump. In this case, however, there is a problem of increase in manufacturing costs through increase of the weight and volume of the hydraulic motor for improving performance of the hydraulic motor. Moreover, the peak of pressure pulsation continuously generated due to operation of the pump can act as a source of noise of the hydraulic brake system.